PC & PLC Hardware Setup and Configuration.

1.    Single PLC to One PC Running TLServer

The simplest configuration will be when there is only one PLC and one PC involved. You simply connect the PLC's RS232 port  to the any of the RS232 serial port (COM1:  to COM8:) of a PC and run the TLServer on it. When you are using TLServer for the first time, you may have to configure TLServer's serial port  to match the communication port number.

2.     Multiple PLCs to One PC Running TLServer

You can connect multiple M-series PLCs to a single PC running TLServer by connecting every PLC's RS485 in a daisy-chain manner to the PC's RS232 port. You do need to purchase a RS232-to-RS485 converter to connect the PC's RS232 port to the RS485 network. Please refer to the PLC's User Manual for details on installation issues regarding electrical specifications and termination requirements when connecting the PLCs in an RS485 network.

Internet TRiLOGI can log-in to the TLServer and have immediate access to all the PLCs on the RS485 network just by specifying the ID address of the PLC concerned. Up to 32 Standard M-series PLCs can be networked to a TLServer.   If you replace the RS485 driver IC by a 1/8 power type you can link up to 255 PLCs to a single TLServer for programming and monitoring!

3.   Networking Consideration

The networking method used by the PC running the TLServer, as well as how the TRiLOGI client software accesses the TLServer will have impact on the configuration of both the TLServer and the TRiLOGI client. We will consider various scenarios below.

1. Standalone PC (No network connection)

If the PC that runs TLServer is a standalone without any network connection, you can still use it for localhost programming. i.e. The PC which is running the TLServer will be the same one that is used to run the TRiLOGI client program.

When you run TLServer you will see that the displayed IP Address is the "localhost" address: 127.0.0.1:9080   (assuming that you did not change the default port = 9080). You can either run the TRiLOGI Application directly or you can open up your web-browser and key in the following URL:  http://127.0.0.1:9080 . In the latter case, you are running TRiLOGI as an applet that is loaded from the TLServer.

2. TLServer has Direct Connection to the Internet

If the PC running the TLServer enjoys a direct connection to the Internet via dial-up, DSL, T1 line  or cable modem, then TLServer will be accessible to any client on the Internet. Note that if you connect to the Internet via dial-up connection, then do remember to connect to the Internet before you run TLServer so that it can report the actual IP address on its front panel.

If the TRiLOGI client software also accesses the Internet via direct connection, you will have the least problem. However, if the TRiLOGI client is sitting behind a corporate firewall, then the situation is much more complex and it has impact on both the TLServer and the TRiLOGI settings, as shown in the following table:

TRiLOGI Client has Direct Internet Connection	TRiLOGI runs on a PC protected by Corporate Firewall
TLServer::  port settings=80 or any value above 1024 TRiLOGI:  "Use HttpProxy" setting is optional	TLServer: Port Settings = 80 TRiLOGI: "Use HttpProxy" = true. May need to obtain proxy server's IP address. See Log-In to TLServer .

What Happens when a Client is behind a firewall but the TLserver has direct link to the Internet?

If the client PC is located within a corporate Intranet and protected by a firewall, then there are very limited means for the client to access the Internet outside of the firewall. Note that NOT all PCs within the LAN have access to the Internet. Whether a PC has access to the Internet or not is decided by your company's System Adminstrator. 

Even if a particular client PC does have access to the Internet (because you are able to use a browser to visit Yahoo!), it doesn't mean that the PC has a direct connection to the Internet. What actually happens is that the network adminstrator has setup a "Proxy Server" or Network Address Translator (NAT)   that will intercept your client PC's request to link to the Internet. The proxy server is the one which actually has a direct link to the Internet. It acts on behalf of the client within the Intranet to process HTTP connection to the Internet and passes the response data to back to the client.

So how does the proxy server determine whether a network packet is meant for the Internet and not meant for another workstation within the Intranet? It determines it by examining the port number that the packet attempts to connect to. If a connection is made to the well known HTTP port which is = 80, it will be handled by the proxy server. If you use a port number such as 9080 (default TLServer port address) it will think that the connection is to be made to some local workstation and hence will not direct the packet via the proxy server to the Internet.

Therefore, in order for the client to make connection to the Internet via the proxy server, the TLServer port address should be set to 80. In addition, the TRiLOGI client should also be configured to access the TLServer via a "Http Proxy Server" as described in the document "Log-In to TLServer".

3. TLServer is on a Local Area Network

If the TLServer is running on a workstation that is part of a local area network, it is unlikely that the workstation will have a direct connection to the Internet (unless the System Adminstrator has deliberately configured it for that purpose). When the TLServer starts, it will report the IP Address of the workstation which is the Intranet IP address and NOT the Internet IP Address.

Now if the TRiLOGI client is  running on another workstation which is also part of the same local area network, then it is quite simple: TLServer can be assigned any unused port number above 1024 and the TRiLOGI client can access TLServer from any other workstations. However, avoid setting TLServer to port 80 since by default, port 80 is for accessing the Internet via the HTTP proxy server.

How to access TLServer running on a Private LAN from the Public Internet?

If the workstation that TLServer is running on does not have a direct Internet connection to the Internet, then it will normally not be possible to access the TLServer via the public Internet since the firewall will block any attempts to access a PC inside the LAN. There are two possible ways to overcome this:

1. Consult your System Adminstrator to configure a Network Address Translator that will assign you a public IP Address which will be mapped to the local workstation that runs the TLServer. If there is a business need for your PLCs to be constantly accessible from the Internet, the System Adminstrator should be able to grant you that permission.

2. If you are using a small home office router (such as Linksys, NetGear etc), you can usually configure these type of routers to "Port Forward" the port number of TLServer (such as 9080) to the PC running the TLServer. Once configured, all internet TCP/IP messages targetting port number 9080 will be automatically forwarded to the predefined PC that runs the TLServer program and you therefore can access the PLC via the public Internet.
   
3. If your  need to provide connectivity from the Internet is only temporary (e.g. allowing your contractor to fix a software bug) it may be easier to use a modem and dial-up to an ISP when the need arises. Once the connection is no longer needed, just hang up the modem. However, before you do this, please check with your company's System Adminstrator to make sure that you are not violating the security policy. If that is a problem, you may consider using a standalone notebook computer or PC (i.e. not connected to the LAN) to make the dial-up connection, which provides temporary Internet connectivity for the TLServer (and hence the PLCs) but will not compromise the security of your corporate Intranet.